Regensburg 2013 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 28: Transport & Diffusion III
MM 28.1: Vortrag
Dienstag, 12. März 2013, 15:00–15:15, H26
7Li NMR field-cycling relaxometry: A powerful tool to investigate lithium ion dynamics in solid-state electrolytes — •Jan Gabriel, Magnus Graf und Michael Vogel — Institut für Festkörperphysik, Technische Universität Darmstadt, Germany
We use 7Li NMR to study lithium ion dynamics in glasses like (Li2S)-(P2S5) and (Li2S)-(GeS2)-(GeO2). Field-cycling relaxometry is employed in combination with stimulated-echo experiments and line shape analysis to cover a time window extending over 10 orders of magnitude. The stimulated-echo method is suitable to measure the correlation functions F2(t) of lithium ion dynamics in solids in a time range from 10−5 to 101 s. Field-cycling relaxometry measures the spectral density J2(ω) from which we obtain a correlation function in a range from 10−9 to 10−5 s. The motional narrowing of NMR spectra is sensitive from 10−4 to 10−5 s. These three methods probe translational motion of the lithium ions. The field-cycling and stimulated-echo data revealed a nonexponentiality of the lithium ion dynamics in the studied glasses. The shape of the spectral density J2(ω) is well described by a Cole-Davidson function and the decay of the correlation function of F2(t) is well interpolated by a Kohlrausch-William-Watts function. Observation of the T1 minimum for a broad range of Larmor frequencies allows us to determine temperature-dependent correlation times and, thus, the activation energy of lithium ion dynamics. When the dynamics of the lithium ions is too slow to be observed at sufficiently low temperatures, field-cycling relaxometry probes the nearly constant loss, which is considered as a universal phenomenon of disordered solids.